Efficiency at light load conditions in voltage converters, e.g., switch mode power supplies (SMPS), is generally improved by the SMPS controller using a pulse frequency modulation (PFM) mode instead of the more standard pulse width modulation (PWM) mode. PWM provides better output voltage regulation but PFM provides greater SMPS efficiency at light current loads. Unfortunately, a side effect of PFM is a larger output ripple voltage that reduces voltage output accuracy. Using a PFM mode for light current loads and a PWM mode for heavier currents would be desirable. However, implementing both PFM and PWM modes in SMPS controllers may require mode transitions with pre-defined and accurate thresholds that may be very difficult to implement in production SMPSs. In addition, a bypass mode may occur when the PWM is on all the time due to high current load.
Mode transition selection may require threshold tuning, and lack adaptive duty control for output voltage accuracy. Present technology solutions to achieve mode transitions may require one or more pre-defined transition thresholds, additional comparators for the PFM mode, additional circuits for bypass mode, and the mode selections may bounce back-and-forth. Also, the PFM mode may become unsynchronized at light loads.